This article describes a dual‐band gap‐filler microstrip antenna with nearly equal gain and similar radiation patterns in the 2.4‐GHz and 5.8‐ GHz ISM satellite Internet service bands.The proposed antenna has two Y‐shaped slots on the microstrip patch and is fabricated on an RO4003 substrate with a dielectric constant of 3.38 and a thickness of 0.508 mm. The dimensions of the antenna are 50 mm × 47.5 mm × 6.5 mm, and it is fed by a coaxial cable. The measured bandwidths of the antenna are 2.376–2.492 GHz and 5.425–6.055 GHz for a voltage standing wave ratio of less than 2. At 2.42 GHz, the antenna has a broadside radiation pattern with a half‐power beamwidth (HPBW) of 70° in the x‐z plane and 80° in the y‐z plane. At 5.75 GHz, it has a HPBW of 65° in the x‐z plane and 75° in the y‐z plane. The measured gain is 8.37 dB in the 2.4‐GHz ISM band and 8.38 dB in the 5.8 GHz ISM band. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1825–1827, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25325